1. Field of the Invention
This invention relates to improved polymer blends of ground vulcanized rubber and polyolefin resin, and in particular, blends of enhanced compatibility due to the presence of a functionalized olefin polymer.
2. Description of the Prior Art
Blends of ground vulcanized rubber and thermoplastic polymer are known. For example, in U.S. Pat. No. 4,028,288, a method is described for preparing mixtures of vulcanized rubber particles and a thermoplastic polymer. However, because of insufficient bonding between the rubber particles and the polymer phase, the resulting compositions exhibited poor mechanical properties, especially low elongation. Therefore, if the compatibility of the blend components can be increased, improved compositions would be obtained.
In U.S. Pat. No. 4,386,182 a thermoplastic elastomeric composition is described, consisting of comminuted vulcanized rubber, a thermoplastic olefin or diolefin polymer, and a compatibilizer additive. This patent, however, is not pertinent to the present invention in that the compatibilizer additive is the reaction product of a hydroxyl compound with an alkene oxide. As will be shown in a comparative example below, the mechanical properties of such composition (e.g. % elongation at break) are inferior relative to the mechanical properties of the compositions of the subject invention.
Each year, in the U.S., more than 240 million used tires are discarded. This, in addition to an estimated 2 billion tires which already exist. Above ground storage of tires presents a fire and health hazard. Once ignited, a pile of tires can burn for months, polluting the air with black smoke and strong odor. Tires constitute an ideal breeding ground for disease carrying mosquitos and rodents. Buried, whole tires settle unevenly and rise to the surface creating landfill management problems. These hazards are well documented in the various tire studies sponsored by the EPA, other federal agencies and state agencies. Both the U.S. Congress and the EPA have previously determined that scrap tires constitute a significant waste management problem. For example, in the 1984 amendment to the Resource Conservation and Recovery Act of 1976, Congress directed EPA to issue procurement guidelines for tires. Many state legislations have enacted or are considering legislation to regulate scrap tire storage and/or disposal. Because of economic and environmental reasons, reclaiming of scrap tires by thermal and/or chemical "devulcanization" has dramatically decreased in recent years. Over the period between 1941 and 1985 consumption of reclaimed rubber has decreased from 32% of new rubber to less than 5%. Burning of tires as fuel has raised concerns about air pollution.